Fix #20763 - Inconsistent handling of type + value in typeof expressions

compiler/src/dmd/expressionsem.d

@@ -14769,11 +14769,16 @@
         return true;
     }
 
-    // FIXME: Existing code relies on adding / subtracting types in typeof() expressions:
-    // alias I = ulong; alias U = typeof(I + 1u);
-    // https://github.com/dlang/dmd/issues/20763
-    if (op == EXP.add || op == EXP.min)
+    if ((op == EXP.add || op == EXP.min) && e.isTypeExp())
+    {
+        // @@@DEPRECATED_2.121@@@
+        // Deprecated in 2.111
+        // In 2.121, remove this branch to let `checkValue` raise the error
+        deprecation(e.loc, "type `%s` has no value", e.toChars);
+        if (!e.type.isOpaqueType)
+            deprecationSupplemental(e.loc, "perhaps use `%s.init`", e.toChars);
         return false;
+    }
 
     return e.checkValue();
 }
@@ -14844,6 +14849,8 @@
     if (auto te = e.isTypeExp())
     {
         error(e.loc, "type `%s` has no value", e.toChars());
+        if (!e.type.isOpaqueType)
+            errorSupplemental(e.loc, "perhaps use `%s.init`", e.toChars());
         return true;
     }
 

compiler/src/dmd/typesem.d

@@ -7609,6 +7609,18 @@
     return false;
 }
 
+/// Returns: whether `t` is a struct/class/enum without a body
+bool isOpaqueType(Type t)
+{
+    if (auto te = t.isTypeEnum())
+        return te.sym.members is null;
+    if (auto ts = t.isTypeStruct())
+        return ts.sym.members is null;
+    if (auto tc = t.isTypeClass())
+        return tc.sym.members is null;
+    return false;
+}
+
 
 /******************************* Private *****************************************/
 

compiler/test/fail_compilation/b17285.d

@@ -1,9 +1,10 @@
 /*
 TEST_OUTPUT:
 ---
-fail_compilation/b17285.d(14): Error: type `ONE` has no value
-fail_compilation/b17285.d(14): Error: type `TWO` has no value
-fail_compilation/b17285.d(14): Error: cannot implicitly convert expression `ONE` of type `b17285.ONE` to `int`
+fail_compilation/b17285.d(15): Error: type `ONE` has no value
+fail_compilation/b17285.d(15):        perhaps use `ONE.init`
+fail_compilation/b17285.d(15): Error: type `TWO` has no value
+fail_compilation/b17285.d(15): Error: cannot implicitly convert expression `ONE` of type `b17285.ONE` to `int`
 ---
 */
 

compiler/test/fail_compilation/ice9545.d

@@ -2,7 +2,8 @@
 /*
 TEST_OUTPUT:
 ----
-fail_compilation/ice9545.d(13): Error: type `int` has no value
+fail_compilation/ice9545.d(14): Error: type `int` has no value
+fail_compilation/ice9545.d(14):        perhaps use `int.init`
 ----
 */
 

compiler/test/fail_compilation/test20763.d

@@ -0,0 +1,31 @@
+/*
+REQUIRED_ARGS: -de
+
+TEST_OUTPUT:
+---
+fail_compilation/test20763.d(25): Deprecation: type `ulong` has no value
+fail_compilation/test20763.d(25):        perhaps use `ulong.init`
+fail_compilation/test20763.d(26): Deprecation: type `ulong` has no value
+fail_compilation/test20763.d(26):        perhaps use `ulong.init`
+fail_compilation/test20763.d(27): Error: type `ulong` has no value
+fail_compilation/test20763.d(27):        perhaps use `ulong.init`
+fail_compilation/test20763.d(28): Error: type `ulong` has no value
+fail_compilation/test20763.d(28):        perhaps use `ulong.init`
+fail_compilation/test20763.d(29): Error: type `ulong` has no value
+fail_compilation/test20763.d(29):        perhaps use `ulong.init`
+fail_compilation/test20763.d(30): Error: type `ulong` has no value
+fail_compilation/test20763.d(30):        perhaps use `ulong.init`
+---
+*/
+
+// https://github.com/dlang/dmd/issues/20763
+void test()
+{
+    alias I = ulong;
+    alias U0 = typeof(I + 1u);
+    alias U1 = typeof(1 - I);
+    alias U2 = typeof(+I);
+    alias U3 = typeof(I * 1);
+    alias U4 = typeof(I << 1);
+    alias U5 = typeof(I | 1);
+}